Partisan divides over the safety of the MMR, flu, and COVID-19 vaccines stem from how Democrats and Republicans view science and scientists, according to a study published this month in the American Journal of Public Health by researchers at the Annenberg Public Policy Center (APPC) of the University of Pennsylvania.
Political Views on Vaccines Differ by Vaccine Type
- The MMR Gap Closes: When researchers accounted for broader views on science, partisan differences in perceptions of measles, mumps, and rubella (MMR) and flu vaccines were no longer statistically significant.
- COVID-19 Stays Polarized: Political affiliation remained significantly tied to COVID-19 vaccine perceptions even after adjusting for views of science.
- Advantage of Science: Believing that science offers advantages regularly correlated with the conviction that all three inoculations were safe and effective.
How Scientific Perceptions Shape Vaccine Acceptance
The study, led by Georgia State University associate professor of communication and APPC distinguished research fellow Dror Walter alongside colleagues at the University at Buffalo and the APPC, analyzed survey data collected in November 2024 from a national probability sample of 1,763 empaneled U.S. adults. When compared to Republicans, Democrats held the view that the measles, mumps, and rubella (MMR), flu, and COVID-19 vaccines carried greater safety and efficacy.
To unpack these gaps, the research team utilized the FASS (Factors Assessing Science’s Self-Presentation) model, originally introduced by APPC researchers in 2023. Rather than asking a blunt question about general trust, the FASS framework evaluates five distinct dimensions: whether respondents consider scientists credible, prudent, and unbiased, and whether they view science as beneficial and self-correcting.
Among these five facets, seeing science as beneficial was consistently associated with confidence in the safety and efficacy of all three vaccines. Other perceptual factors tracked with specific vaccine evaluations.
| Vaccine Evaluated | Average Safety Rating (1–4 Scale) | Average Effectiveness Rating (1–4 Scale) |
|---|---|---|
| Measles, Mumps, and Rubella (MMR) | 3.54 | 3.63 |
| Flu | 3.41 | 3.03 |
| COVID-19 | 2.98 | 2.81 |
Why the COVID-19 Vaccine Breaks the Mold
While statistical adjustments neutralized the partisan gap for the MMR and flu shots, the COVID-19 vaccine resisted this analytical flattening. Even after accounting for respondents’ views on science and scientists, political affiliation remained significantly associated with how individuals judged the COVID-19 inoculation.
“The Covid-19 vaccine really stands apart,” Walter explained. “With MMR and flu, views of science and scientists largely explain the partisan gap in perceptions of vaccines. With Covid-19 they don’t. Something beyond how people see science and scientists is shaping how Democrats and Republicans judge that vaccine.”
The study attributes these divergent trajectories partly to historical context. The MMR vaccine has been widely used for decades. The effectiveness of the seasonal flu vaccine varies seasonally, depending in part on how well the vaccine matches circulating strains.
Conversely, the COVID-19 vaccine was introduced amid an intensely polarized pandemic. It became the subject of attacks by political figures and partisan media, embedding the immunization into broader ideological battles.
Tailoring Public Health Messaging for Divided Audiences
The findings come amid concern among public health experts about vaccine hesitancy and declining childhood vaccination rates. The FASS framework provides a way to pinpoint exact viewpoints useful for directing science communication strategies, as highlighted by Yotam Ophir—an APPC distinguished research fellow who also serves as an associate professor of communication at the University at Buffalo, State University of New York.
“The results of this study, for example, suggest that when communicating about vaccines, in addition to highlighting their effectiveness and safety, we should also inform the public about the tangible benefits of science in general, and vaccines in particular for both individuals and societies,” Ophir stated.
For the COVID-19 vaccine in particular, communication strategies may need to address concerns regarding scientific bias, explaining the mechanisms science uses to identify and correct for bias.
Unresolved Questions in Partisan Health Literacy
While the APPC findings map the contours of political polarization and scientific perception, critical questions remain regarding how to reverse entrenched skepticism. The study’s authors emphasize that future research is needed to test whether such approaches—such as explaining mechanisms to correct for bias—are effective. The study shows that political leaders and the media can shape perceptions of vaccines.
References
- Walter, D., et al. (2026). Dynamics of Political Identity, Scientific Outlooks, and Public Evaluation of MMR, Influenza, and COVID-19 Immunizations in the United States (2024). American Journal of Public Health. DOI: 10.2105/AJPH.2026.308606
Disclaimer: This article is intended for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions regarding a medical condition or vaccination schedule.
